It is known to use gels such as hydrogels based on polysaccharides and water as dermatological fillers. Such gels are generally prepared by methods comprising the chemical cross-linking of the respective polysaccharides in an aqueous medium. Suitable polysaccharides are e.g. based on hyaluronic acid since it is present in identical or similar compositions in each living organism. E.g., hyaluronic acid is a major component of skin, where it is involved in tissue repair. Therefore, it gives a minimum of side effects and allows for safe application.
EP 1 818 344 relates to a process for preparing a crosslinked hyaluronic acid gel, comprising stirring and mixing a mixture containing 10 w/v % or more of hyaluronic acid, a crosslinking agent, and water under acidic or alkaline condition.
EP 2 054 039 (WO 2008/018796) relates to a viscoelastic hydrogel composition comprising first microparticles and second microparticles capable of interacting with each other through stereocomplex interactions, wherein said first microparticles comprise a crosslinked first hydrophilic polymer, said first microparticles comprising external grafts of first oligomers or co-oligomers comprising a first chiral region, said first chiral region comprising first chiral monomers, and wherein said second microparticles comprise a crosslinked second hydrophilic polymer, said second microparticles comprising external grafts of second oligomers or co-oligomers comprising a second chiral region, said second chiral region comprising second chiral monomers, said second chiral monomers having chirality that is opposite to the chirality of said first chiral monomers, wherein said first chiral region and said second chiral region interact with each other non-covalently. The hydrophilic polymer may be hyaluronic acid.
EP 2 178 923 (WO 2009/018076) relates to a process for the preparation of crosslinked hyaluronic acid, said process comprising contacting hyaluronic acid with a polyethylene glycol based crosslinking agent.
WO 2011/119468 relates to a hydrogel for soft tissue augmentation comprising a cross-linked biocompatible polymer having zero-length cross-linked moieties and optionally at least one other active ingredient incorporated into said cross-linked biocompatible polymer.
EP 2 152 329 (WO 2008/068297) relates to an implant that can be injected subcutaneously or intradermally in the form of a single-phase hydrogel comprising a gel composed of crosslinked hyaluronic acid and one of its physiologically acceptable salts.
EP 2 170 961 (WO 2009/021526) relates to a hyaluronic acid dispersion for use in aesthetics medicine and orthopedics, wherein the dispersed phase comprises particles made of crosslinked hyaluronic acid, and the continuous phase substantially comprises linear hyaluronic acid.
EP 1 699 500 (WO 2005/067994) relates to a hyaluronic acid composition comprising crosslinked, water-insoluble, hydrated hyaluronic acid gel particles. The composition may be used for augmenting tissue in a subject that is in need of tissue augmentation, to a method of stabilizing crosslinked HA including hydrating water-insoluble, dehydrated crosslinked HA with a physiologically compatible aqueous solution that includes a local anesthetic, wherein the value of storage modulus G′ for the stabilized composition is at least about 110% of the value of G′ for a non-stabilized composition, and to the stabilized HA composition.
WO 2010/015900 relates to soft tissue fillers, for example, dermal and subdermal fillers, based on hyaluronic acids and pharmaceutically acceptable salts thereof, wherein the hyaluronic acid-based compositions may include a therapeutically effective amount of at least one anesthetic agent, for example, lidocaine. The hyaluronic acid-based compositions including lidocaine have an enhanced stability, relative to conventional compositions including lidocaine, for example when subjected to sterilization techniques or when stored for long periods of time. Methods and processes of preparing such hyaluronic acid-based compositions are also provided.
FR 2 919 999 relates to a cosmetical composition or pharmaceutical composition, which comprises a hyaluronic acid and a divalent cation. The composition may be used for treating wrinkles.
EP 2 254 584 (WO 2009/098127) relates to biocompatible injectable products capable of releasing zinc and/or at least one saccharide salt in the form of zinc, to compositions containing said products, and to the use thereof in particular for filling or increasing the volume of biological tissues or for replacing or supplementing a biological fluid.
EP 2 155 212 (WO 2008/139122) relates to the association of hyaluronic acid and at least one inhibitor of hyaluronic acid degradation, which is intended, in particular, for use in human dermatology and plastic surgery.
EP 0 839 159 B1 discloses a process for preparing a cross-linked biocompatible polysaccharide gel composition. The process comprises the cross-linking of a polysaccharide in the presence of polyfunctional cross-linking agents, wherein a viscoelastic gel is formed.
EP 1 711 552 B1 relates a method for producing a biocompatible crosslinked gel comprising steps of crosslinking a biocompatible polymer, diluting the crosslinked polymer with non-crosslinked polymer, and terminating the crosslinking reaction.
EP 0 466 300 B1 relates to a method of obtaining a biocompatible viscoelastic gel slurry, the method comprising the mixing of a biocompatible gel, which comprises crosslinked hyaluronic acid, with a second polymer, which may e.g. be hyaluronic acid, to form a two phase mixture, and to the gel as such.